000
FXUS61 KPHI 272032
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
332 PM EST MON DEC 27 2010
.SYNOPSIS...
THE INTENSE LOW PRESSURE SYSTEM EAST OF MASSACHUSETTS WILL MOVE
NORTHEAST THROUGH NOVA SCOTIA TONIGHT AND NEWFOUNDLAND ON TUESDAY.
HIGH PRESSURE WILL BUILD TO THE SOUTH OF THE AREA DURING THE MIDDLE
OF THE WEEK, THEN BUILD NORTHEAST ACROSS OUR AREA BY FRIDAY. THE
NEXT LOW PRESSURE SYSTEM IS FORECAST TO PASS WELL NORTHWEST OF THE
AREA ON SATURDAY WITH ITS ASSOCIATED COLD FRONT PASSING THROUGH THE
REGION ON SUNDAY. ANOTHER SOUTHERN PLAINS HIGH PRESSURE SYSTEM
SHOULD THEN MOVE TOWARD THE AREA ON MONDAY.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
THE HEATHER ARCHAMBAULT PATTERN CHANGING WINTER STORM/BLIZZARD WILL
SLOWLY LOSE ITS REMAINING GRIP ACROSS OUR CWA THE NEXT COUPLE OF
DAYS. THE GFS INITIALIZATION LOOKED SLIGHTLY BETTER THAN THE WRF-NMM
AND WE WILL LEAN TOWARD IT THROUGH THE SHORT TERM.
THE WIND ADVISORY HAS BEEN EXTENDED INTO THIS EVENING AS SOME STRONG
WINDS AT 925MB AND 850MB ARE FORECAST TO PERSIST. WHILE MIXING
SHOULD START TO DIMINISH, FROM TIME TO TIME THE POTENTIAL EXISTS
FOR ADVISORY TYPE GUSTS TO MIX DOWN. IN ADDITION, THIS ALSO ALERTS
EVERYONE TO ANY CONTINUED BLOWING SNOW PROBLEMS.
SKIES CLEARED THIS AFTERNOON AND WE CAN SEE THE WESTERN EXTENT OF
OUR LATEST MAJOR WINTER STORM. SOME WEAKENING WAA INDUCED CLOUDS
OVER THE GREAT LAKES SHOULD MAKE IT INTO OUR CWA TONIGHT. IN SPITE
OF FCST POSITIVE OMEGA, THE MOISTURE IS TOO HIGH AND SHALLOW FOR
SNOW TO REACH THE GROUND. THE ONLY EXCEPTION IS OUR FAR NWRN CWA
WHERE A DECENT LAKE EFFECT FETCH IS UNDERWAY. WE WILL HAVE TO
MONITOR HOW SE THEY REACH. THE LATEST HRRR KEEPS MEASURABLE SNOW
NORTH OF OUR BORDER AND FOR NOW WE CARRIED SNOW SHOWERS JUST OVER
THE HIGHER TERRAIN OF THE POCONOS (LATER TONIGHT) AND SOME FLURRIES
FARTHER DOWNSTREAM.
THE CONTINUING WINDS AND FRESH SNOW COVER WILL COMBAT EACH OTHER FOR
HOW LOW WE GET TONIGHT. WE ARE GOING TO GIVE THE EDGE TO THE SNOW
AND SIDE WITH THE LOWER MOS DATASETS.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/...
THE SHORT TERM WILL FEATURE A QUIET WEATHER PERIOD WITH SLOWLY
MODERATING TEMPERATURES. SINCE WE ARE ON THE SUBJECT OF
TEMPERATURES, WE WERE PRETTY CONSERVATIVE WITH MAX TEMPS INTO
THURSDAY SUSPECTING ITS GOING TO BE DIFFICULT TO OBTAIN THE HIGHER
MOS VALUES WITH THE SNOW COVER. THIS IS ESPECIALLY TRUE FROM MORRIS
SOUTHEAST INTO OCEAN COUNTIES WHERE WE WENT WELL BELOW STAT
GUIDANCE. MINS AT NIGHT AT LEAST INITIALLY WILL BE HELD HIGHER BY
THE CONTINUING WIND, BUT BY WEDNESDAY NIGHT, BARRING UNFORECAST
CLOUDS, SHOULD BE PRETTY COLD WITH HIGH PRESSURE PARKED OVER OUR CWA.
WE WENT TOWARD THE LOWER MOS GUIDANCE DATASETS FOR TUE NGT AND NOT
LOWER BECAUSE OF THE POSSIBILITY OF WIND, BUT BELOW ALL THE GUIDANCE
ON WEDNESDAY NIGHT AND CHANCES ARE NOT LOW ENOUGH.
AS FOR THE SENSIBLE WEATHER, THE RETURN FLOW CLOUDINESS SHOULD
DECREASE ON TUESDAY AS PER THE FCST WEAKENING OF THE WAA. THE LAKE
EFFECT FLOW THOUGH WILL BE ONGOING AND WE HAVE ADDED FLURRIES AND
SNOW SHOWERS TO OUR NWRN CWA. WHILE TUESDAY WILL BECOME WINDY
AGAIN, WITH THE STORM NOW HEADING TOWARD NEWFOUNDLAND AND ITS
DEEPENING IN DAYS GONE BY, PEAK WIND GUSTS SHOULD AVERAGE 10 TO 15
MPH LOWER THAN TODAY, WOULD ESTIMATE MOST PEAK WIND GUSTS BETWEEN
30 AND 40 MPH.
THE LAKE EFFECT FLOW IS EXPECTED TO BECOME MORE WESTERLY
TUESDAY NIGHT WHICH SHOULD SHUT OFF THE RESIDUALS FROM REACHING OUR
NWRN CWA. THE WRF-NMM REMAINS MORE BULLISH ABOUT TRAPPED SC THAN THE
GFS N. GOING ON MODEL TENDENCIES WE WENT TWO-THIRDS TOWARD THE
WRF-NMM SOLUTION. AS HIGH PRESSURE MOVES CLOSER TO OUR CWA ON
WEDNESDAY AND CONVECTIVE TEMPS FCST TO BE TOUGHER TO REACH, THE
FORECAST IS FOR A SUNNIER DAY. SOME CIRRUS MIGHT FLY OVER THE
SURFACE RIDGE ON WEDNESDAY NIGHT AND THURSDAY, BUT OTHERWISE MOSTLY
CLEAR/MOSTLY SUNNY SKIES WILL PREVAIL WITH CONSIDERABLY LIGHTER
WINDS BY THEN.
&&
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
5-WAVE MODEL GUIDANCE SHOWS A LONG-WAVE TROUGH OVER THE
INTER-MOUNTAIN WEST STATES CORRESPONDING TO A WEAK MID-LEVEL RIDGE
OVER THE EAST COAST. THE TROUGH SHOULD BEGIN TO MOVE TOWARDS THE
EAST WHICH IN TURN WILL FLATTEN THE RIDGE OVER THE EAST AS A MORE
ROBUST REX BLOCK TRIES TO SET UP OVER GREENLAND ONCE MORE.
THE LONG-TERM BEGINS WITH SURFACE AND MID-LEVEL RIDGING NOSING INTO
THE REGION FROM THE WEST AND SLIDING TO OUR EAST LATE ON FRIDAY.
THIS WILL ALLOW FOR AN UPWARD TREND IN OUR TEMPERATURES ON FRIDAY
AND SATURDAY AS THE RETURN FLOW SETS UP AND 850MB TEMPERATURES CLIMB
TO ABOVE 0F FOR THE FIRST TIME IN QUITE A WHILE. WE COULD COME CLOSE
TO SEEING 50F ACROSS THE METRO AREA ON NEW YEARS DAY, ALTHOUGH THIS
BRIEF RESPITE IS JUST THAT...BRIEF.
LOW PRESSURE SKIRTING BY TO OUR NORTH WILL PUSH THROUGH A COLD FRONT
ON LATE SATURDAY NIGHT SPILLING INTO SUNDAY. WE COULD SEE A MIX OF
RAIN/SNOW ON SATURDAY NIGHT WHICH SHOULD THEN CHANGE OVER TO ALL
RAIN ON SUNDAY. AS THE FRONT GOES THROUGH AND MOVES OFFSHORE WE WILL
ONCE AGAIN EXPERIENCE A BRISK NORTHWEST FLOW AND TEMPERATURES WILL
DROP INTO THE 30S FOR THE REMAINDER OF THE PERIOD. WINDS WILL PICK
UP ONCE AGAIN ON SUNDAY AND MONDAY.
&&
.AVIATION /21Z MONDAY THROUGH SATURDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
THE GRADIENT BETWEEN THE DEPARTING (BUT STILL STRENGTHENING) LOW
PRESSURE SYSTEM AND AN INCOMING HIGH PRESSURE SYSTEM FROM THE
MISSISSIPPI RIVER VALLEY WAS PRODUCING WIND GUSTS OVER 40 KT AT
SEVERAL TAF SITES MONDAY AFTERNOON. MODELS INDICATE A VERY GRADUAL
WEAKENING OF THIS PRESSURE GRADIENT TONIGHT THROUGH TUESDAY, SO BOTH
THE SUSTAINED WINDS AND THE WIND GUSTS SHOULD ALSO GRADUALLY WEAKEN
DURING THIS SAME TIME PERIOD. ALSO, MIXING WILL DECREASE AFTER
SUNSET WHICH WILL DAMPEN THE TRANSPORT OF 925H WINDS DOWN TO THE
SURFACE. SO, GUSTS SHOULD DROP FROM NEAR 40 KT TO PERHAPS 35 KT THIS
EVENING...THEN TO 30 KT OR SO BY TUESDAY MORNING. WIND DIRECTION IS
EXPECTED TO REMAIN IN THE 280 TO 330 QUADRANT THROUGH THE TAF
PERIOD.
BLOWING SNOW WAS BEING REPORTED AT SEVERAL TAF SITES THIS MORNING
AND EARLY AFTERNOON. THIS MAY CONTINUE TO BE AN ISSUE INTO THE
EVENING HOURS TONIGHT, BUT THEN SHOULD LESSEN AS THE WINDS VERY
SLOWLY WEAKEN.
OUTLOOK...
HIGH PRESSURE WILL BUILD INTO OUR REGION FROM THE WEST AND DOMINATE
OUR WEATHER LATE TUESDAY THROUGH THE FIRST PART OF THE UPCOMING
WEEKEND.
&&
.MARINE...
WINDS OVER THE MARINE AREA HAVE NOW SUBSIDED SUFFICIENTLY TO
DOWNGRADE THE STORM WARNINGS OVER OUR NORTHERN COASTAL WATERS TO
GALE WARNINGS. HOWEVER...WIND GUSTS OVER 34 KT ARE EXPECTED THROUGH
THE OVERNIGHT HOURS AS THE PRESSURE GRADIENT IS FORECAST TO RELAX
ONLY EVER SO SLOWLY THROUGH TUESDAY...SO GALE WARNINGS WILL REMAIN
IN PLACE. THE ONE EXCEPTION MAY BE THE UPPER DELAWARE BAY WHERE THE
DAMPENING OF TRANSPORT WINDS AFTER SUNSET MAY REDUCE WIND GUSTS TO
JUST BELOW GALE. LATER SHIFTS CAN EVALUATE THIS SITUATION AND MAKE
NECESSARY ADJUSTMENTS.
WAVE HEIGHTS HAVE PEAKED AND ARE EXPECTED TO GRADUALLY LOWER OVER
THE NEXT SEVERAL DAYS.
HIGH PRESSURE WILL PUSH IN FROM THE WEST TUESDAY AND DOMINATE OUR
WEATHER THROUGH THURSDAY...STILL HAVING INFLUENCE FRIDAY. WEST TO
NORTHWEST WINDS WILL CONTINUE TO GUST TO OVER 25 KNOTS THROUGH
TUESDAY, BUT MAY DROP BELOW ADVISORY CRITERIA TUESDAY NIGHT.
SUB-ADVISORY WINDS AND SEAS WERE FORECAST FOR WEDNESDAY THROUGH
FRIDAY.
&&
.TIDES/COASTAL FLOODING...
TIDE LEVELS ARE NOW BACK TO NORMAL AT MOST GAGE LOCATIONS AND SO
TIDAL FLOODING IS NO LONGER A CONCERN. HOWEVER...WITH THE STRONG
NORTHWEST FLOW...NEGATIVE TIDAL ANOMALIES CAN BE EXPECTED OVER THE
NEXT DAY OR SO. WHILE THESE NEGATIVE ANOMALIES ARE NOT EXPECTED TO
PRODUCE BLOWOUT TIDE CONDITIONS ATTM...THE SITUATION WILL BE
MONITORED AND APPROPRIATE PRODUCTS ISSUED IF NEEDED.
&&
.CLIMATOLOGY...
WHILE BIG TICKET SNOW STORMS HAVE BECOME MORE COMMON OF LATE, IT IS
RARE FOR THEM TO OCCUR WHEN A MODERATE OR STRONG LA NINA IS
OCCURRING IN THE TROPICAL PACIFIC. THIS IS ONLY THE SECOND TIME SINCE
SNOW RECORDS HAVE BEEN KEPT IN PHILADELPHIA (SINCE 1884) THAT A
FOOT OR MORE OF SNOW OCCURRED IN A SINGLE EVENT DURING A MODERATE
OT STRONG LA NINA WINTER. THE PREVIOUS ONE WAS 21.0 INCHES ON
DECEMBER 25-26, 1909. IN THIS INSTANCE THE NEGATIVE NORTH ATLANTIC
OSCILLATION TRULY TRUMPED THE LA NINA WHICH IN GLOBAL ATMOSPHERIC
TERMS HAS NOT BEEN BEHAVING LIKE ONE ACROSS NORTH AMERICA SINCE
DECEMBER STARTED. THE HEATHER ARCHAMBAULT THESIS OF LARGE
PRECIPITATION EVENTS AT PATTERN CHANGE TIME RANG TRUE AGAIN AND A
MORE TYPICAL LA NINA SCENARIO IS ABOUT TO OCCUR ACROSS NOAM DURING
THE NEXT ONE TO TWO WEEKS.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...WIND ADVISORY UNTIL 10 PM EST THIS EVENING FOR PAZ054-055-
060>062-067>071.
NJ...WIND ADVISORY UNTIL 10 PM EST THIS EVENING FOR NJZ001-007>010-
012>027.
DE...WIND ADVISORY UNTIL 10 PM EST THIS EVENING FOR DEZ001>004.
MD...WIND ADVISORY UNTIL 10 PM EST THIS EVENING FOR MDZ008-012-015-
019-020.
MARINE...GALE WARNING UNTIL 3 PM EST TUESDAY FOR ANZ430-431-450>455.
&&
$$
SYNOPSIS...DELISI/GIGI
NEAR TERM...GIGI
SHORT TERM...GIGI
LONG TERM...HEAVENER
AVIATION...MIKETTA
MARINE...MIKETTA
TIDES/COASTAL FLOODING...MIKETTA
CLIMATOLOGY...GIGI
